The Solar Orbiter spacecraft captures the full sun like never before

Animation of ESA’s Sun-Explorer Solar Orbiter. Credit: ESA / Medialab

Recent images of the Solar Orbiter show the full sun in unprecedented detail. They were taken on March 7, 2022, when the spacecraft passed directly between Earth and the Sun.

One of the images taken by Extreme Ultraviolet Imager (EUI) is the highest resolution image of the full disk of the sun and the corona of the outer atmosphere.

Another image taken by the Spectral Imaging of the Coronal Environment (SPICE) instrument represents the first full-fledged solar image of its kind in 50 years, and is the finest photograph taken at the Lyman-beta wavelength of the emitted ultraviolet light. Hydrogen gas.

Pictures taken when the Solar Orbiter was about 75 million kilometers away, half the distance between our world and its parent star. The EUI’s high-resolution telescope requires a mosaic of 25 individual images to cover the full sun at that close distance. The whole picture taken one after the other took more than four hours because each tile took about 10 minutes, including the time it takes for the spacecraft to move from one section to the next.

The solar orbiter captures the sun in intense ultraviolet light

The sun is viewed by the solar orbit in ultraviolet light from a distance of about 75 million kilometers. This image is a mosaic of 25 unique images taken on March 7, 2022, using the Extreme Ultra Violet Imager (EUI) high resolution telescope. Taken at a wavelength of 17 nanometers in the ultraviolet region of the electromagnetic spectrum, this image reveals the corona, the upper atmosphere of the Sun, with a temperature of about one million degrees Celsius. At 2 o’clock, a picture of the earth is also added for size. Credit: ESA & NASA / Solar Orbiter / EUI Group; Data Processing: E. Kraaikamp (ROB)

Overall, The The final picture The 9148 x 9112 pixel grid has more than 83 million pixels. In comparison, this image has ten times better resolution than what can be seen on a 4K TV screen.

The EUI captures the Sun at a wavelength of 17 nanometers in the ultraviolet region of the electromagnetic spectrum. It exposes the upper atmosphere of the sun, which has a temperature of one million degrees[{” attribute=””>Celsius.

Taking the Sun’s Temperature

Solar Orbiter took images of the Sun on March 7, from a distance of roughly 75 million kilometres, using its Spectral Imaging of the Coronal Environment (SPICE) instrument. SPICE takes simultaneous “spectral images” at several different wavelengths of the extreme ultraviolet spectrum by scanning its spectrometer slit across a region on the Sun. The different wavelengths recorded correspond to different layers in the Sun’s lower atmosphere. Purple corresponds to hydrogen gas at a temperature of 10,000°C, blue to carbon at 32,000°C, green to oxygen at 320,000°C, yellow to neon at 630,000°C. Each full-Sun image is made up of a mosaic of 25 individual scans. It represents the best full Sun image taken at the Lyman beta wavelength of ultraviolet light that is emitted by hydrogen gas. Credit: ESA & NASA/Solar Orbiter/SPICE team; Data processing: G. Pelouze (IAS)

At the 2 o’clock (near the image of the Earth for scale) and 8 o’clock positions on the edges of the Sun, dark filaments can be seen projecting away from the surface. These ‘prominences’ are prone to erupt, throwing huge quantities of coronal gas into space and creating ‘space weather’ storms.

In addition to EUI, the SPICE instrument was also recording data during the crossing. These too needed to be pieced together as a mosaic.

SPICE is designed to trace the layers in the Sun’s atmosphere from the corona, down to a layer known as the chromosphere, getting closer to the surface. The instrument does this by looking at the different wavelengths of extreme ultraviolet light that come from different atoms.

Taking the Sun’s Temperature

Taking the Sun’s temperature. Credit: ESA & NASA/Solar Orbiter/SPICE team; Data processing: G. Pelouze (IAS)

In the SPICE sequence of images purple corresponds to hydrogen gas at a temperature of 10,000°C, blue to carbon at 32,000°C, green to oxygen at 320,000°C, yellow to neon at 630,000°C.

This will allow solar physicists to trace the extraordinarily powerful eruptions that take place in the corona down through the lower atmospheric layers. It will also allow them to study one of the most puzzling observations about the Sun: how the temperature is rising through the ascending atmospheric layers.

Usually the temperature drops as you move away from a hot object. But above the Sun, the corona reaches a million degrees Celsius whereas the surface is only about 5000°C. Investigating this mystery is one of the key scientific objectives of Solar Orbiter.

ESA Solar Orbiter Facing Sun

ESA’s Solar Orbiter. Credit: ESA/ATG medialab

The images were taken on 7 March, precisely when Solar Orbiter crossed the Sun-Earth line, so the images can be compared with Earth-bound solar instruments and cross-calibrated. This will make it easier to compare results from different instruments and observatories in future.

On March 26, Solar Orbiter reaches another mission milestone: its first close perihelion. The spacecraft is now inside the orbit of Mercury, the inner planet, taking the highest resolution images of the Sun it can take. It is also recording data on the solar wind of particles that flows outwards from the Sun.

And this is just the start, over the coming years the spacecraft will repeatedly fly this close to the Sun. It will also gradually raise its orientation to view the Sun’s previously unobserved polar regions.

Solar Orbiter is a space mission of international collaboration between ESA and NASA.

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